Conventional ball grid array (BGA) electronic packages typically experience substrate trace crack failure after temperature cycling in certain applications. The substrate trace crack failure is often significant enough to pose a reliability risk to BGA electronic packages. One specific example relates to when memory BGA package are mounted onto very stiff printed circuit boards (PCBs).
Existing BGA ball pads have a round shape. The round shape of the BGA ball pads creates a tangential crack at the ball pad edge when the BGA ball pads are exposed to stress. Failure analysis shows that cracks in the substrate core material and/or solder mask are formed tangential to the edge of the round BGA ball pad.
Prior attempts to address substrate trace crack problems include (i) using low coefficient of thermal expansion substrate materials; (ii) designing wider traces at critical routing locations; and (iii) implementing larger diameter glass fiber materials in substrates in order to enhance substrate mechanical properties. However, these previous solutions usually only serve to block (not eliminate) the crack propagation that is commonly caused by stressing the BGA ball pads. In addition, each of these prior solutions typically has other limitations (e.g., cost and/or inhibition of high volume manufacturing).